Positioning stage having a vibration suppressor

Abstract

A first stage adapted to be moved in predetermined directions by a first driving device is provided in a machine base supported from a foundation by an intermediary of resilient means. This first stage is provided a second stage adapted to be moved in the directions at right angles to the directions of movement of the first stage by a second driving device. Upon movement of these respective stages, vibration of the machine base is excited by reaction forces exerted upon the machine base as a result of acceleration and deceleration. These reaction forces are offset by resistive forces generated by first and second force generators respectively. The first and second force generators establish an electromagnetic coupling between the foundation and the machine base. The first force generator is made to act against the first driving device, and the second force generator is made to act against the second driving device, in such manner that the first and second force generators generate forces directed in the opposite directions to and having substantially the same magnitudes as the reaction forces exerted upon the machine base by the first and second driving devices, respectively. This occurs simultaneously with energization of the corresponding driving devices and effectively suppresses vibration of the machine base.

What is claimed is: 
     
       1. A precision positioning device having a vibration suppressor comprising: a foundation;   a machine base;   a means for resiliently supporting said machine base on said foundation;   a first positioning stage and a second positioning stage disposed on said machine base, said first and second positioning stages being mounted for movement in first and second predetermined directions, respectively, relative to said machine base;   a first electromechanical driving device and a second electromechanical driving device disposed on said machine base, said first and second electromechanical driving devices being adapted for driving said first and second stages in said first and second predetermined directions, respectively, said first and second driving devices thereby creating undesirable reaction forces on said base relative to said first and second predetermined directions, respectively; and   a first force generator and a second force generator establishing an electromagnetic coupling between said foundation and said base, said first and second force generators each comprising:   (i) a means for generating an electromagnetic field associated with one of said foundation and said base; and   (ii) a conductive coil disposed within the electromagnetic field established by said means for generating, said coil being associated with the other of said foundation and said base; whereby, a first control current and a second control current applied to the coils of said first and second force generators, respectively, provide resistive forces which are substantially equal to and in opposite directions to said undesirable reaction forces thus suppressing vibration of said precision positioning device created by said first and second electomagnetic driving devices, said first and second control currents being proportional to the driving currents applied to said first and second electromagnetic driving devices, respectively.